Transfer switch for tap-changing transformers having contacts movable along orthogonal diameters of a circle



Sept. 3, 1968 A. BLEIBTREU 3,400,231

TRANSFER SWITCH FOR TAP-CHANGING TRANSFORMERS HAVING CONTACTS MOVABLE ALONG ORTHOGONAL DIAMETERS OF A CIRCLE Filed Jan. 25, 1966 3 Sheets-Sheet l b Q as It i-l? Imam roe mm BMW A. BLEIBTREU 3,400,231 -CHANGI NG TRANSFORMERS HAVING CONTACTS GONAL DIAMETERS OF A CIRCLE 3 Sheets-Sheet 2 7 Sept. 3, 1968 TRANSFER SWITCH FOR TAP MOVABLE ALONG ORTHO Filed Jan. 25, 1966 lm zwrof' WAMMMM MA Wm M Wm W Sept. 3, 1968 BLElBTREu 3,400,231

TRANSFER SWITCH FOR TAP-CHANGING TRANSFORMERS HAVING CONTACTS MOVABLE ALONG ORTHOGONAL DIAMETERS OF A CIRCLE Filed Jan. 25, 1966 5 Sheets-Sheet 5 United States Patent 3,400,231 TRANSFER SWITCH FOR TAP CHANGING TRANSFORMERS HAVING CONTACTS MOV- ABLE ALONG ORTHOGONAL DIAMETERS OF A CIRCLE Alexander Bleibtreu, Regensburg, Germany, assignor to Maschinenfabrik Reinhausen Gebruder Schenbeck K.G., Regensburg, Germany Filed Jan. 25, 1966, Ser. No. 522,908 Claims priority, application Germany, Feb. 23, 1965, M 64,282 9 Claims. (Cl. 200-11) ABSTRACT OF THE DISCLOSURE Disclosed below is a transfer switch for effecting tapchanging operations allowing a relative increase of the stroke of its movable contacts and a relative decrease of its bulk. This is achieved by contact means having trajectories which are orthogonal diameters of a circle, and by operating means capable of moving the contact means along these trajectories in any desired sequence.

This invention has reference to load tap-changers for power transformers as applied, for instance, to maintain a constant secondary voltage with a variable primary voltage.

It is a general object of this invention to provide improved load tap-changers.

A further object of this invention is to provide load tapchangers which are considerably more compact than comparable prior art load tap-changers.

Load tap-changers include selector switches and transfer switches. The selector switches serve the purpose of se lecting a particular tap on a tapped transformer winding intended to be connected into an electric circuit. Selector switches do not carry any load currents at the time a particular tap is selected, i.e., they are not required to interrupt or close on current-carrying circuits. This task is performed by the transfer switches. The latter perform all switching operations under load. Therefore all arcing is restricted to the transfer switches, the selector switches 'merely selecting the particular transformer tap to which the load is to be transferred.

This invention relates more specifically to transfer switches for load tap-changers, one of its principal objects being to provide transfer switches that combine long strokes of the movable contacts thereof with extremely small overall dimensions and extremely small overall bulk.

It is common practice to subdivide polyphase load tapchangers into separate units. Each such single-phase unit comprises a separate tank, a separate single-phase transformer, a separate single-phase selector switch, a separate single-phase transfer switch and separate drives for the latter. A plurality of such single-phase units are integrated into a polyphase transformer.

-It is, therefore, another object of this invention to provide single-phase units which are less bulky than the 3,400,231 Patented Sept. 3, 1968 Load tap-changers utilizing ohmic resistors as currentlrrnlting devices and fast operating transfer switches are known, or referred-to, as Jansen type load tap-changers. This type of load tap-changers has important advantages over load tap-changers of other kinds. In Jansen type tap-changers the movable contacts of the transfer switches move at high speeds, or with a snap action into, and out of, engagement with the fixed contacts to some of which current-limiting resistors are connected. As a result of this fast motion, the transition periods during which the current-limiting resistors must carry load currents are very short, say in the order of a few hundredths of a second. This has two significant advantages: The current-limiting resistors may be small, and the voltage fluctuation resulting from tap-changes insignificant. The rapid operation of the transfer switches is produced by stored energy means, preferably wound-up springs which are maintained in a pre-wound, or pre-loaded condition in readiness for the next tap-changing operation. Load tap-changers of the Jansen type are well known in the art and have been described in many printed publications.

It is another object of this invention to provide improved transfer switches for Jansen type load tap changers.

The foregoing and other general and special objects of theinvention and advantages thereof will appear more clearly from the ensuing particular description of the invention as illustrated in the accompanying drawings, wherein FIG. 1 is a top plan view of a transfer switch embodying this invention;

FIG. 2 is generally a side elevation of the structure of FIG. 1 showing some portions thereof in vertical section;

FIG. 3 is a diagrammatic top-plan view of the structure of FIG. 1 including the circuitry which is associated with it; and

FIGS. 4a to 4d show diagrammatically consecutive positions of the constituent parts of the structure of FIG. 3 during a tap-changing operation.

The transfer switch shown in the drawings is a transfer switch intended for a single-phase circuit. It comprises fixed main contacts 1, 4 and fixed auxiliary contacts 2, 3. These contacts are preferably arranged in pairs, i.e., there is an upper fixed main contact 1 and a lower fixed main contact 1; an upper fixed main contact 4 and a lower fixed main contact 4; an upper fixed auxiliary contact 2 and a lower fixed auxiliary contact 2; and an upper fixed auxiliary contact 3 and a lower fixed auxiliary contact 3. Each pair of fixed contacts 1, 1; 4, 4; 2, 2 and 3, 3 is supported by a vertical substantially rod-shaped contact support 5 of insulating material. Upper fixed main contact 1 and upper fixed auxiliary contact 3 are arranged adjacent opposite ends of a first diameter of a circle. Upper fixed main contact 4 and upper fixed auxiliary contact 2 are arranged adjacent opposite ends of a second diameter of said circle at substantially right angles to the aforementioned first diameter thereof. The same arrangement applies to the lower fixed main contacts 1, 4 and to the lower fixed auxiliary contacts 2, 3. Reference numerals 6 and 7 have been applied to indicate a pair of spaced, parallel, horizontal plates. Plates 6 and 7 may be shaped more or less like a star, as clearly shown in FIG. 1. The upper ends of the four contact supports 5 of insulating material for fixed contacts 1, 2, 3, 4 are secured to the upper plate 6, which may be effected by screws 6a. The lower ends of the four contact supports 5 of insulating material are secured to the lower plate 7 by appropriate fasteners such as, for instance, screws 7a. The upper plate 6 and the lower plate 7 are each provided with a pair of slots to which reference numeral 8 has been applied. These slots are substantially coextensive with the aforementioned diagonals extending between the pair of fixed main and auxiliary contacts 1, 3 and the pair of fixed main and auxiliary contacts 4, 2.

The transfer switch further comprises movable contact means generally indicated by reference characters 9, 10. Contact means 9 is adapted to move along one of the above diagonals from fixed main contact 1 to fixed auxiliary contact 3, and vice versa. Contact means is adapted to move along the other of the above diagonals from fixed main contact 4 to fixed auxiliary contact 2, and vice versa. Contact means 9, 10 are in the nature of contact bridges conductively interconnecting upper and lower pairs of fixed contacts 1, 1; 3, 3; 4, 4; 2, 2 whenever in the appropriate position. Each movable contact means 9, 10 includes a contact support 11 of insulating materialclearly shown in longitudinal section on the left side of FIG. 2and a pair of bridge contacts 12, 13 arranged on opposite sides of contact support 11. Reference numeral 14 has been applied to indicate the fulcra at which bridge contacts 12, 13 are pivotally supported by contact supports 11 and reference numeral 15 has been applied to indicate leaf springs interposed between the ends of bridge contacts 12, 13 and contact supports 11. Each bridge contact 12, 13 has a limited freedom of pivotal movement about its fulcrum 14. Contact supports 11 include guide elements 16 and 17 arranged at the upper ends thereof and at the lower ends thereof. Guide elements 16 engage slots 8 in upper plate 6 and slide along said slots. Guide elements 17 engage the slots 8 in lower plate 7 and slide along said slots. The length of parts 16 and 17 in the direction of the slot in which the respective part is arranged exceeds the depth of slots 8. As a result parts 16, 17 are securely guided inside of slots 8 at all points thereof, including the area 18 where slots 8 intersect.

As best shown in FIG. 1 the contact means 9, 10 or their contact supports 11 are tied together by an integral pair of four-bar-linkages to which reference characters 19 and 20 have been applied. Reference character 21 has been applied to indicate the center fulcrum of the integral pair of four-bar-linkages in the form of identical parallelograms. Helical spring 22 is secured with one end thereof to fulcrum 21, and with the other end thereof to the end 23 of a lever or arm 24. There is one integral pair of four-bar-linkages 19, 20 arranged above plate 6, and another integral pair of four-bar-linkages 19, 20 arranged below plate 7. The lower intergal pair of four-bar-linkages 19, 20 is connected by a spring 22 to the end 23 of a lever or arm 25 in the same fashion as the upper integral pair of four-bar-linkages 19, 20 is connected to the end 23 of lever 24. Levers or arms 24, 25 are supported by a vertical drive or operating shaft 26 arranged midway between fixed contacts 1 and 4. Drive shaft 26 is am eccentric shaft considering the intersection 18 of slots 8 to be the center of the transfer switch. Plates 6 and 7 are provided with bearings 6b and 7b, respectively, supporting operating shaft 26. The latter may be operated by a loaded spring, not shown, as common in Jansen type transfer switches. Such a spring may be adapted to be wound-up manually, or by means of an electric motor, as desired.

In FIGS. 3 and 4a to 4d the same reference characters have been applied as in FIGS. 1 and 2 to indicate like parts. Reference character Tr has been applied in FIG. 3 to indicate a winding of a single-phase transformer having but two taps U U Actually the number of taps will be larger than two, and this requires to interpose a conventional selector switch between the tapped winding of the transformer and the transfer switch. Since such switches are common practice and well known prior art, and since the explanation of the operation of the transfer switch embodying this invention can be simplified by assuming that the transformer winding Tr has but two taps and by deleting a selector switch, but two taps have been shown in FIG. 3, and a selector switch deleted in this figure.

It is apparent from FIG. 3 that the two fixed main contacts 1 and 4 are directly connected by appropriate leads to taps U and U Where a transfer switch includes pairs of fixed main contacts 1 and 4, i.e., an upper and a lower fixed main contact, the lower fixed main contacts may be directly connected by appropriate leads to taps U and U and the upper fixed main contacts 1 and 4 and the upper fixed auxiliary contacts 2 and 3 short-circuited. The point establishing a short-circuit between the upper fixed contacts 1', 2,3, 4 of the transfer switch is the neutral point of the circuitry. It will be apparent from FIG. 3 that the lower fixed main contact 1 is directly connected by a lead to tap U and the lower fixed main contact 4 is directly connected by a lead to tap U Lower fixed auxiliary contact 3 is connected by the intermediary of a first impedance, or ohmic resistor R, shown to the right of FIG. 3, to tap U and lower fixed main contact 4, respectively. Lower fixed auxiliary contact 2 is connected by the intermediary of a second impedance, or ohmic resistor R, shown to the left of FIG. 3, to tap U and lower fixed main contact 1, respectively. I

As shown in FIG. 3 the bridge contacts 12 of the movable contact means 9 conductively interconnect fixed main contacts 1, and the bridge contact 12 of movable contact means 10 conductively interconnect the fixed auxiliary contacts 2. In that position of the transfer switch all the upper fixed contacts 1, 2, 3, 4 of the transfer switch are at the potential of tap U After completion of a tap changing operation all the upper fixed contacts 1, 2, 3, 4 of the transfer switch will be at the potential of tap U The tap-changing operation is initiated by pivoting shaft 26 and arms or levers 24, 25 in clockwise direction, as indicated in FIGS. 1 and 3 by a clockwise arrow. As a result, springs 22 interposed between linkages 19, 20 and arms or levers 24, 25 are stressed and displaced in the way indicated in FIG. 4a. When shaft 26 and levers 24, 25 reach and are moved beyond a critical positionthe over-center position thereofmovable contact means 9 moves with a snap action along one of the aforementioned diagonals out of engagement with fixed main contacts 1 and into engagement with fixed auxiliary contacts 3. FIG. 4b shows the position of the constituent parts of the transfer switch when bridge contacts 13 conductively interconnect fixed auxiliary contacts 3 as a result of the aforementioned initial clockwise operation of shaft 26.

It will be apparent that fixed auxiliary contacts 2 are conductively interconnected during the aforementioned switching step, and that at the end of the aforementioned switching step the fixed auxiliary contacts 2 and the fixed auxiliary contacts 3 are conductively interconnected.

When shaft 26 and levers or arms 24, 25 are further turned in clockwise direction, springs 22 are again displaced and stressed, this time in the way shown in FIG. 40. When shaft 26 and levers or arms 24, 25 reach and move beyond another over-center position thereof, contact means 10 moves with a snap-action from its left limit position shown in FIG. 40 to its right limit position shown in FIG. 4d. In other words, contact means 10 snaps along one of the aforementioned diagonals out of engagement with fixed auxiliary contacts 2 and into engagement with fixed main contacts 4, the latter position beingshown in FIG. 4d. In the position shown in FIG. 4d the bridge contact 13 interconnects conductively the fixed main. contacts 4. This terminates the tap changing operation from tap U to tap U The aforementioned switching or tap changing operation from tap U totap U is reversed if shaft 26 and levers or arms 24, 25 are moved in counterclockwise direction, as seenin FIGS. 1 and 3. a

It is apparent from the foregoing that the switching mechanism according to the invention is capableof performing the same switching operations as prior art Jansen type transfer switches, but that linkage mechanism of the instant transfer switch is considerably less elaborate than that in prior art Jansen type transfer switches. It

will also be noted that the instant transfer switch requires a smaller number of movable contacts than needed in prior art Jansen type transfer switches, i.e., but two movable contacts instead of at least four movable contacts. It will further be apparent that the contact travel or stroke of the movable contacts is relatively long in spite of the great compactness of the instant transfer switch. The long travel or stroke of the movable contacts is conducive to a rapid dielectric'recovery of the gaps formed between the parting contacts of the transfer switch, and to a high degree of dielectric strength of thesegaps when the movable contacts have completed their respective travel or stroke and are in the limit positions thereof. Transfer switches according to this invention are smaller than prior art transfer switches having the same rating, and are particularly suited for high power applications. In this context the term main contact has been applied with reference to contacts in a transfer switch making it possible to establish a direct current path from a tap of a tapped transformer winding to a load circuit terminal without insertion of an impedance (e g., resistor) into that current path. The term auxiliary contact has been applied with reference to contacts in a transfer switch making it possible to interpose an impedance (e.g., resistor) into the current path from a tap of a tapped transformer winding to a load circuit terminal.

Having fully described my invention and illustrated a preferred embodiment thereof it will be understood that various changes may be made in the structure shown by those versed in the art without departing from the spirit and scope of my invention; hence I do not intend to be limited by the exemplary preferred embodiment illustrated, but what I claim as new and wish to secure by Letters Patent is:

1. A transfer switch for tap-changing regulating transformers comprising:

(a) fixed contacts arranged along the periphery of a circle, said fixed contacts including a first fixed main contact and a first fixed auxiliary contact arranged adjacent opposite ends of a first diameter of said circle and said fixed contacts further including a second fixed main contact and a second fixed auxiliary contact arranged adjacent opposite ends of a second diam eter of said circle at substantially right angles to said first diameter of said circle;

(b) means for conductively connecting said first fixed main contact to a first tap of a transformer winding;

(c) means for conductively connecting said second fixed main contact to a second tap of said transformer winding;

(d) means including a first impedance for conductively connecting said first fixed auxiliary contact to said second tap of said transformer winding;

(e) means including a second impedance for conductively connecting said second fixed auxiliary contact to said first tap of said transformer winding;

(f) a first movable contact means guided to move in the direction of said first diameter of said circle along a path extending between said first fixed main contact and said first fixed auxiliary contact;

(g) a second movable contact means guided to move in the direction of said second diameter of said circle along a path extending between said second fixed main contact and said second fixed auxiliary contact; and

(h) operating means for said first movable contact means and operating means for said second movable contact means for moving said first movable contact means along said first diameter and for moving said second movable contact means along said second diameter in any desired sequence.

2. A transfer switch for tap-changing regulating transformers as'specified in claim 1 comprising:

(a) fixed contacts arranged along the peripheries of a pair of coaxial circles situated in parallel planes,

said fixed contact means including a first fixed main contact and a first fixed auxiliary contact arranged adjacent opposite ends of a first diameter of one of said pair of circles, said fixed contacts further including a second fixed main contact and a second fixed auxiliary contact arranged adjacent opposite ends of a second diameter of said one of said pair of circles at substantially right angles to said first diameter of said one of said pair of circles, said fixed contacts further including a first fixed main contact and a first fixed auxiliary contact arranged at opposite ends of a first diameter of the other of said pair of circles, and said fixed contacts further including a second fixed main contact and a second fixed auxiliary contact arranged adjacent opposite ends of a second diameter of said other of said pair of circles at substantially right angles to said first diameter of said other of said pair of circles;

(b) means for conductively connecting one of said first fixed main contacts to a first tap of a transformer winding;

(0) means for conductively connecting one of said second fixed main contacts to a second tap of a transformer winding;

(d) means including a first impedance for conductively connecting one of said first fixed auxiliary contacts to said second tap of a transformer winding;

(e) means including a second impedance for conductively connecting one of said second fixed auxiliary contacts to said first tap of a transformer winding;

(f) a first movable contact means for selectively conductively interconnecting said first fixed main contacts and said first fixed auxiliary contacts;

(g) means for guiding said first movable contact means along a first straight path intermediate said first fixed main contacts and said first fixed auxiliary contacts;

(h) a second movable contact means for selectively conductively interconnecting said second fixed main contacts and said second fixed auxiliary contacts;

(i) means for guiding said second movable contact means along a second straight path intermediate said second fixed main contacts and said second fixed auxiliary contacts at substantially right angles to said first path; and

(j) operating means for said first movable contact means and for said second movable contact means for mov ing said first movable contact means along said first path and for moving said second movable contact means along said second path in any desired sequence.

3. A transfer switch as specified in claim 1 wherein said first movable contact means includes a pair of separate contact elements each supported by a first common contact support of insulating material and arranged on opposite surfaces thereof, and wherein said second movable contact means includes a pair of separate contact elements each supported by a second common contact support of insulating material and arranged on opposite surfaces thereof.

4. A transfer switch as specified in claim 2 wherein said first movable contact means includes a pair of separate contact bridges each supported by a first common substantially rod-shaped contact support of insulating material and arranged on opposite surfaces thereof, and wherein said second movable contact means includes a pair of separate contact bridges each supported by a second common substantially rod-shaped contact support of insulating material and arranged on opposite surfaces thereof.

5. A transfer switch as specified in claim 4 comprising a pair of parallel spaced plates each defining a pair of slots angularly displaced degrees, said first common contact support engaging with the ends thereof one of said pair of slots in each of said pair of plates and said second common contact support engaging with the ends thereof the other of said pair of slots in each of said pair of plates.

6. A transfer switch as specified in claim 5 wherein each of said pair of slots in each of said pair of plates has a predetermined width and wherein said ends of said first common contact support have a predetermined thickness in the direction of said first pair of diameters and said ends of said second common contact support each have a predetermined thickness in the direction of said second pair of diameters, said predetermined thickness exceeding said predetermined width.

7. A transfer switch as specified in claim 1 comprising common operating means for said first movable contact means and for said second movable contact means, said common operating means including an integral pair of four-bar-linkages having one end tied to said first movable contact means and another end tied to said second movable contact means, a driving lever pivotable about a point radially spaced from the point of intersection of said first diameter and said second diameter, and spring means interposed between said pair of four-bar-linkages and said driving lever. p I

8. A transfer switch as specified in claim 7 including a driving shaft supporting said driving lever, said driving shaft being equally spaced from said first fixed main contact and from said second fixed main contact.

9. A transfer switch as specified in claim 7 wherein said spring means is attached to said four-bar-linkage at a point midway between the endsthereof.

References Cited UNITED STATES PATENTS 2,680,790 6/1954 Jansen 200-11 2,691,079 10/1954 Jansen 20011 3,250,865 5/1966 Bleibtreu 200-11 ROBERT K. SCHAEFER, Primary Examiner.

H. BURKS, Assistant Examiner. 

